Permanent injury to the central nervous system (CNS) occurs in a variety of medical conditions, and has been the subject of intense scientific scrutiny in recent years. It is known that the brain has high metabolic requirements, and that it can suffer permanent neurologic damage if deprived of sufficient oxygen (hypoxia) for even a few minutes. In the absence of oxygen (anoxia), mitochondrial production of ATP cannot meet the metabolic requirements of the brain, and tissue damage occurs. This process is exacerbated by neuronal release of the neurotransmitter glutamate, which stimulates NMDA (N-methyl-D-aspartate), AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionate) and kainate receptors. Activation of these receptors initiates calcium influx into the neurons, and production of reactive oxygen species, which are potent toxins that damage important cellular structures such as membranes, DNA and enzymes.
The brain has many redundant blood supplies, which means that its tissue is seldom completely deprived of oxygen, even during acute ischemic events caused by thromboembolic events or trauma. A combination of the injury of hypoxia with the added insult of glutamate toxicity is therefore believed to be ultimately responsible for cellular death. Hence if the additive insult of glutamate toxicity can be alleviated, neurological damage could also be lessened. Anti-oxidants and anti-inflammatory agents have been proposed to reduce damage, but they often have poor access to structures such as the brain (which are protected by the blood brain barrier).
Cannabinoid receptors are important in the regulation of Fcγ receptor responses of monocytes and macrophages. Cannabinoid receptors are expressed on lung epithelial cells. These cells are responsible for the secretion of mucins and inflammatory cytokines/chemokines in the lung and are thus intricately involved in the generation and progression of respiratory diseases. Cannabinoid receptors may be expressed on gut epithelial cells and hence regulate cytokine and mucin production and may be of clinical use in treating inflammatory diseases related to the gut. Cannabinoid receptors are also expressed on lymphocytes, a subset of leukocytes.
Up to now, two subtypes of cannabinoid receptors and a splice variant have been identified. The CB1 receptor (Nature 1990, 346, 561) and a splice variant CB1a (J. Biol. Chem. 1995, 270, 3726) are mainly localized in the central nervous system. The CB2 receptor was mainly found in the peripheral tissue, in particular in leucocytes, spleen and macrophages (Eur. J. Biochem. 1995, 232, 54). CB1 and CB2 receptors have seven transmembrane regions and belong to the family of G protein receptors. Both receptors are negatively coupled via Gi/Go protein to adenylate cyclase and possibly negatively coupled to the presynaptic release of glutamate [cf. J. Neurosci. 1996, 16, 4322]. CB1 receptors are moreover positively coupled to potassium channels and negatively coupled to N- and O-type calcium channels.
Brain injury, such as, cerebral apoplexy is a result of a sudden circulatory disorder of a human brain area with subsequent functional losses, with corresponding neurological and/or psychological symptoms. The causes of cerebral apoplexy can lie in cerebral hemorrhages (e.g. after a vascular tear in hypertension, arteriosclerosis and apoplectic aneurysms) and ischemias (e.g. due to a blood pressure drop crisis or embolism). The functional losses in the brain lead to a degeneration or destruction of the brain cells. After a cerebral vascular occlusion, only a part of the tissue volume is destroyed as a direct result of the restricted circulation and the decreased oxygen supply associated therewith. This tissue area designated as the infarct core can only be kept from dying off by immediate recanalization of the vascular closure, e.g. by local thrombolysis, and is therefore only limitedly accessible to therapy. The outer peripheral zone, also designated as the penumbra, also discontinues its function immediately after onset of the vascular occlusion, but is initially still adequately supplied with oxygen by the collateral supply and irreversibly damaged only after a few hours or even only after days. Since the cell death in this area does not occur immediately, a therapeutic opportunity reveals itself to block the unfavorable development of the course of the disease both after stroke and after trauma. However, without early diagnosis, the prognosis of such patients is poor.
There is thus, a need in the art appropriate, specific, inexpensive and simple diagnostic clinical assessments of nervous system injury severity and therapeutic treatment efficacy. Thus identification of neurochemical markers that are specific to or predominantly found in the nervous system (CNS (brain and spinal cord) and PNS), would prove immensely beneficial for both prediction of outcome and for guidance of targeted therapeutic delivery.